Area Forecast Discussion
Issued by NWS Portland, ME

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404 FXUS61 KGYX 242254 AFDGYX Area Forecast Discussion National Weather Service Gray ME 654 PM EDT Tue Apr 24 2018 .SYNOPSIS... Low pressure moves north into the area Wednesday and Wednesday night allowing rain to overspread the area from the southwest in the morning and work northeast by afternoon. A good soaking rain is expected for most of the region. This system will slowly exit the region Thursday. A cold front on Saturday will bring colder air back into the area, with a freeze possible by Sunday morning for some of the area. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
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655 PM Update...Have updated the forecast - mainly for latest trends in temperatures and sky cover. Clouds continue to increase this evening with winds diminishing. Dry weather is expected through much of the night. Previously... Strong upper ridge continues strong subsidence keeping skies clear across the region into the evening. Mid/high clouds will spill through the ridge from west-east later tonight ahead of the approaching low pressure system from the mid atlantic region. Models similar on timing overall, spreading rain across NH after midnight and into southwest Maine toward morning. The increase in cloud cover and developing south to southeast onshore flow will combine to help keep temps mild tonight with lows mostly in the 40s.
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&& .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... Models agree on lifting the upper trof with its associated surface low northeast across the region Wed and Wed night. Soaking rains can be expected with QPF in the .75 to 1.5 inches range. RFC QPF guidance appears reasonable and accepted. With snowmelt in the mountains combining with the rainfall, some area river flows may approach flood stage. Temps will be much cooler Wed due to the rain and onshore flow with highs only reaching into the upper 40s and lower 50s. Meanwhile overnight lows Wed will stay in the mid to upper 40s. && .LONG TERM /THURSDAY THROUGH TUESDAY/...
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The 500 MB trend across NOAM ans surrounding bodies of water will trend toward a somewhat less blocky patter, as closed lows separate from the nrn stream and allow a more zonal flow, with warmer air moving pole ward toward our latitude. This will not happen quickly, and will still have to deal with one trough that cools things down over the weekend, but overall, no major systems in the area, and perhaps a more significant warming trend next week. Thursday will see weakening 500 MB track NE as sfc low tracks across the CWA in the morning. Showers and some light rain will be lingering into the morning, but should see showers become more infrequent and maybe some breaks of sun in the south during the afternoon. Highs will be in the mid 50s to upper 50s across most of the cwa, but southern NH could see temps rise into the low 60s. Some lingering showers will be possible in the mountains Thu night, but for the most part should see some clearing everywhere, with lows in the upper 30s N to mid 40s S. Models agree, in principle, that another sfc wave develops in response to deepening 500 MB wave to our N, and will bring a round of showers through NEw England somewhere in the Fri-Sat nite time period. Chc pops are included for all these periods for now, and will move up to likely pops once there`s a better signal as to when this system moves thru. Temps will remain fairly near normal in this time frame with highs in the upper 50s to mid 60s and lows in the mid 30s to mid 40s Friday and Saturday. It will turn briefly colder behind this system Sunday into Monday, with temps running a little below normal, and highs mainly in the 50s Sunday, and slightly warmer on Monday. The 12Z Euro keep up with the promise of a big warm ridge building over the wrn Atlantic and pumping in some very warm air by the middle of next week, which is supported by the GFS, although not quite as warm.
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&& .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... Short Term...VFR conditions thru tonight. Rain spreads from south to north Wed reducing conditions to IFR. Long Term...Thu morning will start with IFR or lower, but should see improvement to MVFR /or VFR in the south/ during the afternoon. VFR is expected Thu night into FRiday morning, but may see conds deteriorate to MVFR, or even IFR at times late Friday into Saturday. && .MARINE...
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Short Term...Winds and seas will remain below SCA thresholds tonight after a few gusts around 25 kt this evening. Increasing onshore flow Wed afternoon will allow winds and seas to build to SCA thresholds over the outer waters and continue through Wednesday night. Long Term...Seas will remain high through the day Thu despite weakening winds. The waters should remain quiet Fri and Sat, but may approach SCA in W flow behind a cold front Sat night into Sunday.
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&& .FIRE WEATHER... Tonight cool temps and good RH recovery. Wednesday into early Thursday widespread soaking rain is expected and will significantly reduce the fire danger. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory from 5 PM Wednesday to 8 PM EDT Thursday for ANZ150-152-154. && $$

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